Variation plus the calibrated 10 dB external attenuator cor
rection factor must not exceed 0.3 dB. (If Digital Storage is
provided, activate B-SAVE A to obtain the differential. De
activate SAVE A and B-SAVE A.)
Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Performance Check
h. Since the remaining 60 dB range of the RF
ATTENuator is obtained by the combination of these three
attenuators, this completes the check of the RF attenuator.
Error of any combination must not exceed 0.7 dB.
e. Readjust the signal generator output to establish a
new reference level. Repeat the process to check the 20 dB
attenuator by switching the REF LEVEL from -3 0 dBm to
-10 dBm for 20 dB ATTEN, then remove 20 dB of external
attenuation. Error must not exceed 0.6 dB.
f. Reinstall the 30 dB of external attenuation and set the
REF LEVEL to -30 dBm. Re-establish a signal reference
level as described above.
g. Check the 30 dB attenuator against the external stan
dard, by switching the REF LEVEL to 0 dBm, for 30 dB RF
ATTEN, then remove 30 dB of external attenuation. Error
must not exceed 0.7 dB. (Include the calibrated attenuator
correction factor.)
5. Check IF Gain Accuracy (±0.2 dB/dB and
±0.5 dB/10 dB to a maximum of ±2 dB over the full
90 dB range, 70 dB for a non-Option 03 instrument)
NOTE
This check requires calibrated attenuators as the
standard to check the 10 dB and 1 dB steps. When
making signal measurements within 10 dB of the
noise floor, a correction factor should be used to cor
rect for the logarithmic addition o f noise in the system
and analyzer, as shown in Table 3-3.
Signal Source
+30 dBm to —80 dBm
100 kHz to 10 GHz
492 Spectrum Analyzer
o o o
Calibrated Attenuators
10 dB & 20 dB
O
Q
Calibrated 10 dB and 1 dB step attenuators
or separate 10 dB and 1 dB attenuators.
Fig. 3-3. Test equipment setup for verifying attenuator and gain accuracy.
3-12
REV AUG 1981
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